Linking horizontal and vertical transports of biomass fire emissions to the Tropical Atlantic Ozone Paradox during the Northern Hemisphere winter season: 1999

The horizontal and vertical transport of biomass fire emissions in West Africa for January 1999, are examined using all available data including wind, fire, aerosol, precipitation, lightning and outgoing longwave radiation. Ozonesonde data from the Aerosols99 Trans-Atlantic cruise are also included with rain and wind analyses. The results here support earlier studies that ozone and ozone precursors associated with biomass burning are confined to the lower troposphere primarily due to the lack of deep convection over land areas. Ozone and its precursors are horizontally transported equatorward or toward the west by winds in the 1000-700 hPa layers. However, rising adiabatic motions associated with the diurnal evolution of the West African planetary boundary layer can transport ozone and its precursors vertically into the free troposphere above the marine boundary layer. Moreover, lightning from South America, Central Africa and mesoscale convective systems in the Gulf of Guinea can lead to elevated ozone mixing ratios in the middle and upper troposphere of the tropical south Atlantic. The results presented here shed light of the proposed ozone paradox during Northern Hemisphere winter.